JP5790028B2 - Manufacturing method of ferro-coke for metallurgy - Google Patents

Description

  The present invention relates to a method for producing ferro-coke for metallurgical use in which ferro-coke is produced by molding a mixture of a carbonaceous material and iron ore and subjecting the produced molded product to carbonization.

  In order to reduce the reducing material ratio of the blast furnace, it is effective to reduce the temperature of the heat storage zone formed in the blast furnace (for example, see Non-Patent Document 1).

As a method for lowering the temperature of the heat preservation zone, there is a method of lowering the starting temperature of the coke gasification reaction (endothermic reaction) represented by the following formula (1).
C + CO ₂ → 2CO (1)
Ferro-coke produced by dry distillation of a molded product obtained by mixing carbonaceous material (coal) and iron ore increases the CO ₂ reactivity of coke in ferro-coke by the catalytic effect of reduced iron ore. The ratio of the reducing material can be reduced by the accompanying decrease in the temperature of the heat preservation zone (see, for example, Patent Document 1).

  As a technique for producing such ferro-coke, a method has been studied in which powder iron ore is blended with raw coal, and a mixture obtained by mixing is subjected to dry distillation in a normal chamber-type coke oven. For example, (a) a method in which a powder mixture of coal and fine iron ore is charged into a chamber-type coke oven, (b) coal and iron ore are molded cold, that is, at room temperature, and the molded product is chamber-type It is a method (for example, refer nonpatent literature 2) of charging to a coke oven.

  In addition, a method has been proposed in which a coal and iron ore molded product is carbonized in a vertical type carbonization furnace instead of a chamber furnace type coke oven (see Non-Patent Document 3).

Since expressing the effect of increasing the CO ₂ reactivity of the coke in the iron oxide, even if iron ore are all not be reduced to metallic iron, the effect of increasing the CO ₂ reactivity is estimated to be (non-patent document 4 reference.).

On the other hand, regarding normal coke charged in a blast furnace, it is considered that the CO ₂ reactivity is improved as the dry distillation temperature is lower (for example, see Non-Patent Document 5).

JP 2006-28594 A

Japan Iron and Steel Association "Iron and Steel" 87, 2001, p. 357 Fuel Association "Coke Technology Annual Report" 1958, p. 38 “JFE Technical Review” 22, 2008, p. 20 “Fuel” 65, 1986, p. 1476 Japan Iron and Steel Association "Iron and Steel" 68, 1982, S-744 “Kawasaki Steel Technical Report” 6, 1974, p. 16

In order to further reduce the reducing material ratio of the blast furnace, ferro-coke is used in the blast furnace as described above, and the catalytic effect of the reduced iron ore increases the CO ₂ reactivity of the coke in the ferro-coke, The storage zone temperature needs to be lowered. However, the optimum ferro-coke production conditions for increasing the CO ₂ reactivity of coke in ferro-coke are not clear. Furthermore, it is desirable to evaluate the CO ₂ reactivity of coke under conditions that take into account the blast furnace conditions.

This invention is made | formed in view of the said subject, Comprising: The objective is in the ferro-coke in a blast furnace when manufacturing ferro-coke by dry-distilling the mixture which consists of a carbonaceous material and iron ore. An object of the present invention is to provide a metallurgical ferro-coke manufacturing method capable of increasing the CO ₂ reactivity of coke, thereby lowering the heat preservation zone temperature and reducing the reducing material ratio.

The features of the present invention for solving such problems are as follows.
(1) A method for producing a ferro-coke by molding a mixture of carbonaceous material and iron ore to form a molded product, and subjecting the molded product to dry distillation, wherein the maximum temperature of the ferro-coke during the dry distillation is 800 A method for producing ferro-coke for metallurgy, characterized in that the temperature is from 900C to 900C.
(2) The method for producing ferro-coke for metallurgy according to (1), wherein the maximum temperature of ferro-coke during the carbonization is 800 ° C. or higher and 850 ° C. or lower.
(3) The ferro-coke manufacturing method according to (1) or (2), wherein the ferro-coke has a particle size of 15 mm or more and 35 mm or less.
(4) The ferro-coke manufacturing method according to (3), wherein a particle size of the ferro-coke is 15 mm or more and 28 mm or less.
(5) The ferro-coke manufacturing method according to any one of (1) to (4), wherein the ferro-coke has an iron content of 5 to 40% by mass.
(6) Any one of (1) to (5), wherein dry distillation of the molding is performed in a vertical furnace, and the top gas of the vertical furnace is used as a gas for heating the molding. The ferro-coke manufacturing method as described in one.

According to the present invention, ferro-coke having high CO ₂ reactivity in the blast furnace can be produced, and the reducing material ratio of the blast furnace can be further reduced due to a decrease in the temperature of the heat preservation zone. In addition, since the dry distillation temperature is not increased more than necessary when producing ferro-coke, it can contribute to the optimization of the required heat quantity.

It is a schematic diagram which shows the shape of ferro-coke. It is a graph which shows the relationship between the ferro-coke dry distillation temperature and the reduction rate of iron in ferro-coke. It is a graph which shows the time difference in which the particle | grain surface layer and center become the same temperature in temperature rising process. It is a graph which shows the descent speed required in order that a particle | grain surface layer and a center may become the same temperature. It is a graph which shows an ore particle size distribution. It is a graph which shows the relationship between the ferro-coke particle size and the ventilation resistance of the mixed layer of an ore and ferro-coke. It is a graph which shows the ferro coke reaction test conditions. It is a graph showing the relationship between the CO ₂ reactivity of ferro coke carbonization temperature and carbon. It is a graph which shows the relationship between the iron content in ferro-coke, and reaction start temperature. It is a graph which shows the relationship between the ferro-coke dry distillation temperature and the reducing material ratio of a blast furnace at the time of using ferro-coke.

In order to increase the CO ₂ reactivity of coke in ferro-coke, the present inventors have developed a ferro-coke used for blast furnace operation that is produced by dry distillation of a molded product obtained by molding a mixture of carbonaceous material and iron ore. The coke production method was examined and considered as follows.

  (A) Since the reduction of the mixed iron ore proceeds as the temperature of the ferro-coke at the time of dry distillation increases, the catalytic effect increases.

(B) On the other hand, since coke is generally considered to improve CO ₂ reactivity as the temperature of coke at the time of dry distillation is lower, attention is also paid to the coke portion where carbonaceous material is carbonized, which is a part other than iron of ferro-coke, The reactivity of the coke portion in ferro-coke is improved as the dry distillation temperature is lower.

That is, when the temperature of ferro-coke at the time of dry distillation at the time of producing ferro-coke increases, the CO ₂ reactivity of coke may be improved from the viewpoint of the catalytic effect of reduced iron, and from the viewpoint of coke characteristics, CO ₂ reactivity may be reduced. Therefore, in order to increase the CO ₂ reactivity of coke, it is considered that there is an optimum temperature range in the ferro-coke production conditions.

Therefore, the present inventors conducted an experiment to evaluate the CO ₂ reactivity of coke by changing the temperature conditions and dry-distilling ferro-coke under the conditions in which the gas and temperature in the blast furnace were reproduced. ₂ The dry distillation conditions of ferro-coke that enhance the reactivity were derived. The process will be described below.

Ferro coke is a mixture of coal and iron ore (coal is 90, 80, 70, 60 mass%, iron ore is 10, 20, 30, 40 mass%) molded by a briquette machine (briquette). It was produced by dry distillation in a pressure dry distillation furnace. The shape of the briquette is shown in FIG. In FIG. 1, the top is a plan view of the briquette, and the bottom is a front view, and L = 30 mm, B = 25 mm, and T = 18 mm. L is length (length), B is width (breadth), T is thickness (thickness), and the particle size of ferro-coke is (length × width × thickness) ^1/3 , that is, (L × B × T) ^1/3

  The temperature of ferro coke at the time of dry distillation (ferro coke dry distillation temperature) was 750, 800, 850, 900, 950 ° C. The ferro-coke dry distillation temperature is the highest temperature during dry distillation, and the temperature at the center of the briquette is measured. The temperature was raised to 5 ° C./min up to these maximum temperatures and held at the maximum temperature for 90 minutes. The atmosphere was a mixed gas of 30% hydrogen, 11% carbon monoxide, 17% carbon dioxide, 21% nitrogen, 5% water vapor, and 16% methane (each vol%). This is based on the premise of continuous production using a gas-solid counter-current moving bed using a vertical furnace in actual ferro-coke production, and further assumes a process using furnace top gas as gas. FIG. 2 shows the reduction rate of ferro-coke medium iron ore at each ferro-coke carbonization temperature. As the ferro-coke distillation temperature rises, the reduction rate increases.

  Next, the effect of the particle size of ferro-coke on productivity was examined. It is desirable to keep the temperature in the briquette uniform during dry distillation, especially with regard to the maximum temperature that greatly affects the properties of the product. When using a vertical dry distillation furnace that is a countercurrent moving bed of gas and solid, it is necessary to set operating conditions so as to ensure a time for the temperature to be uniform in the briquette.

In FIG. 3, the time difference from when the surface layer reached 850 ° C. until the center reached 850 ° C. was measured when the briquette volume was changed and the temperature was raised from 25 ° C. to 850 ° C. at a heating rate of 5 ° C./min. Results are shown. The briquette volume of 6 cm ³ was used as a reference condition, and the relative values with respect to the briquette volume of 6 cm ³ were arranged. The atmosphere was a mixed gas of hydrogen 30%, carbon monoxide 11%, carbon dioxide 17%, nitrogen 21%, water vapor 5%, methane 16% (each vol%), and the temperatures of the briquette surface layer and the center were measured. As the briquette volume increases, the time for the entire briquette to reach a uniform temperature increases.

Next, we examined the operating conditions of the dry distillation furnace necessary to bring the entire briquette to a uniform temperature. Based on the condition of the briquette volume of 6 cm ³ , the time for holding the whole particle at a uniform temperature for the briquette larger than 6 cm ³ , that is, the time for holding the whole particle at 850 ° C. after the briquette center reaches 850 ° C. is the same. In order to achieve this, an extra time is required as compared to the time when the entire 6 cm ³ briquette shown in FIG. As a means for adjusting the time, there is a change in the briquette descending speed. A briquette with a volume of 6 cm ³ , a zone length of 1.5 m at 850 ° C. and a transit time of 90 minutes. The briquette volume and the entire briquette are dry-distilled at 850 ° C. based on the briquette descending speed of 1 m / hour. FIG. 4 shows the relationship between the briquette lowering speeds necessary for the time taken to be equal. As the briquette volume increases, it is necessary to lower the descent rate. This means a decrease in production rate. When the volume is 6 cm ³ , the production rate decreases by 5% or more when the volume exceeds 14 cm ³ . As described above, when the particle size of ferro-coke is represented by (length × width × thickness) ^1/3 , the particle size of volume 6 cm ³ is 23.8 mm and the particle size of 14 cm ³ is 28.3 mm. The particle size of 18 cm ³ corresponds to 30.6 mm. As described above, the briquette having a small particle size is more advantageous in terms of productivity. However, assuming use in a blast furnace, it is desirable to define a lower limit to the particle size from the viewpoint of air permeability.

Ferro-coke is desirably used by being mixed with an iron raw material composed of sintered ore, pellets, lump ore and the like. Hereinafter, an iron raw material composed of sintered ore, pellets, lump ore and the like is referred to as ore. At this time, since maintaining the air permeability of the mixed layer of ore and ferro-coke is important for operation, the effect of the particle size of ferro-coke on the air-flow resistance of the mixed layer of ore and ferro-coke was investigated. The ferro-coke ratio in the ore was 21 vol% (corresponding to a ferro-coke ratio of 35 mass%). The particle size distribution of the ore is shown in FIG. The change in ventilation resistance due to the particle size of the ferro-coke mixed in the ore was calculated using the following formula (2).
Ventilation resistance index = (1 / Φdp) ^1.3・ (1-ε) ^1.3 / ε ³ (2)
Here, Φ is the shape factor (0.7), dp is the average particle size of the ore / ferrocoke mixed layer, and ε is the porosity of the ore / ferrocoke mixed layer. The average diameter of the mixed layer was calculated by correcting the particle size distribution shown in FIG. 5 according to the assumed ferrocoke particle size, and the porosity was estimated from the corrected particle size distribution (see Non-Patent Document 3). The results are shown in FIG. It can be seen that when the particle size of ferro-coke is between 15 and 35 mm, the ventilation resistance is low and the change is small. If the particle size of the ferro-coke is less than 15 mm, the average diameter of the mixed layer is lowered to increase the airflow resistance. On the other hand, the airflow resistance increases even under the condition that the particle size of the ferrocoke is large, but this is due to the decrease in the porosity due to the expansion of the particle size distribution. From the above, it was found that the ferrocoke particle size is preferably 15 to 35 mm in order to avoid an increase in ventilation resistance. In the case of ferrocoke having a shape as shown in FIG. 1 manufactured using a molding machine, the particle size (= (L × B × T) ^1/3 ) of ferrocoke as defined above is 15 to 35 mm. It is desirable to be. More desirably, the thickness is 20 to 35 mm.

  From the above, the particle size of ferro-coke is preferably 28 mm or less from the viewpoint of securing productivity of the dry distillation furnace, and 15 to 35 mm from the viewpoint of air permeability when using the blast furnace. In consideration of both securing of productivity and air permeability, a range of 15 to 28 mm is desirable.

Briquettes have names such as Macek type, Indo type, egg type, and oval type depending on the shape of the mold of the briquetting machine. In any case, the three symmetry axes (L, B, T mentioned above) ), The characteristic is defined by the particle size (= (L × B × T) ^1/3 ) shown above.

  Next, a test was conducted in which ferrocoke produced at 750, 800, 850, 900, and 950 ° C. ferrocoke dry distillation temperatures was reacted under conditions simulating blast furnace conditions. The briquette shape was L = 30 mm, B = 25 mm, and T = 18 mm in FIG. The reaction conditions are shown in FIG. In FIG. 7, the part indicated by a thick line corresponds to a condition that reproduces the history that the charge received when the charge descends from the top of the blast furnace to the temperature range of 1200 ° C.

  FIG. 8 shows the relationship between the ferro-coke dry distillation temperature and the reaction rate of carbon in the ferro-coke for ferro-coke after the reaction to 1200 ° C. under the conditions of FIG. The reaction rate was low when the ferro-coke dry distillation temperatures were 750 ° C. and 950 ° C., and the maximum value was obtained at 850 ° C. When the ferro-coke distillation temperature is 750 ° C., the reduction rate of iron ore in ferro-coke is as low as 20% as shown in FIG. 2, and it is assumed that the reactivity is low because the catalytic effect of reduced iron is small. . In addition, as shown in FIG. 2, the reduction rate of iron ore in ferrocoke increases as the ferrocoke dry distillation temperature increases, but the reactivity decreases at 950 ° C. due to the decrease in the reactivity of the coke part. Presumed.

  Moreover, the reaction start temperature in the said test of the ferro-coke manufactured by changing iron content into 0-40 mass% and having a carbonization temperature of 850 degreeC is shown in FIG. Here, the temperature at which the reaction rate of carbon in ferrocoke reached 0.8% was defined as the reaction start temperature. According to FIG. 9, as the iron content in the ferro-coke increases, the reactivity is improved and the reaction start temperature is lowered. And a big effect is expressed from iron content 5 mass%, and an effect is saturated at 40 mass% or more. From this, it can be said that 5-40 mass% is a desirable iron content. Therefore, the iron content in ferrocoke is preferably 5 to 40% by mass, more preferably 10 to 40% by mass.

From the above, when producing ferro-coke by dry distillation of a mixture of carbonaceous material and iron ore, the temperature of ferro-coke at the time of dry distillation is in the range of 800-900 ° C, desirably 800-850 ° C. It was found that ferro-coke having high CO ₂ reactivity can be produced by setting the temperature within the range, particularly desirably around 850 ° C.

  The particle size of ferro-coke is preferably 28 mm or less from the viewpoint of ensuring productivity of the dry distillation furnace, and 15 to 35 mm from the viewpoint of air permeability when using the blast furnace. Considering both productivity and air permeability, 15 to 28 mm is desirable.

  The iron content in the ferrocoke is preferably 5 to 40% by mass, more preferably 10 to 40% by mass. As the carbon material, coal is preferably used. In addition to coal, biomass and the like can also be used.

  A blast furnace use test of ferro-coke produced under each dry distillation temperature condition was conducted.

  Ferro-coke continuously dry-distilled briquettes obtained by molding a mixture of coal and iron ore (coal is 70 mass%, iron ore is 30 mass%) with a briquette machine in a gas heating vertical distillation furnace. The gas used is one obtained by heating a part of the top gas of the carbonization furnace (hydrogen 30 vol%, carbon monoxide 11 vol%, carbon dioxide 17 vol%, nitrogen 21 vol%, water vapor 5 vol%, “methane + ethane” 16 vol%), The temperature of the briquette was increased by forming a countercurrent moving layer with the gas rising in the dry distillation furnace and the briquette descending continuously in the furnace. The briquette dimensions were as shown in FIG. 1 (L = 30 mm, B = 25 mm, T = 18 mm). In a vertical distillation furnace, the briquette charged from the top of the furnace is heated to around 600 ° C. in about 1 hour, but from 600 ° C. to the maximum temperature, the temperature is raised from 2 ° C./min to 5 ° C./min, Hold at maximum temperature for 1.5 hours. This maximum temperature was taken as the ferro-coke dry distillation temperature. Here, for example, as shown in Non-Patent Document 6, a difference occurs between a gas temperature and a solid temperature in a vertical-type dry distillation furnace. Taking this difference into consideration, a heat transfer simulation of the countercurrent moving bed was performed, and the gas conditions were adjusted so that the solid temperature was a predetermined condition.

  Table 1 shows ferro-coke production conditions (ferro-coke dry distillation temperature), iron reduction rate in ferro-coke, operating conditions (ferro-coke consumption, chamber coke ratio, pulverized coal ratio) and blast furnace operation results (reducing material ratio). The relationship between the ferro-coke dry distillation temperature and the blast furnace reducing material ratio is shown in FIG. In Table 1, in the case of normal blast furnace operation without using ferro-coke, the base is a case where Cases 1 to 5 are performed by uniformly mixing ferro-coke into the ore layer and charging from the top of the blast furnace.

  According to Table 1, it can be seen that the reducing material ratio can be reduced by using ferro-coke against the condition (base) in which ferro-coke is not used. In particular, when the temperature of ferro-coke at the time of dry distillation (ferro-coke dry distillation temperature) is between 800 and 900 ° C., the reducing agent ratio can be reduced by 30 kg / t or more. It is estimated that this is due to the interaction between the effect of increasing the function as a catalyst because the reduction rate of iron in ferro-coke increases as the carbonization temperature increases, and the effect of reducing the reactivity of the coke part as the carbonization temperature increases. Is done.

Claims (3)

Molding a mixture of charcoal and iron ore to form a molding,
The molded product is to be carbonized in a vertical furnace,
Using the top gas of the vertical furnace as a gas for heating the molded product, a method for producing ferro-coke used in a blast furnace,
The ferro-coke has 10-40 mass% iron,
The method for producing ferro-coke for metallurgy, wherein the maximum temperature of ferro-coke at the time of carbonization is 800 ° C. or higher and 850 ° C. or lower.
However, the case where the maximum temperature of the ferro-coke is 800 ° C. is excluded.   The ferro-coke manufacturing method according to claim 1, wherein the ferro-coke has a particle size of 15 mm or more and 35 mm or less.   The ferro-coke manufacturing method according to claim 2, wherein a particle size of the ferro-coke is 15 mm or more and 28 mm or less.

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